Explanation of Threes and Layups NBA Net Rating Calculator


Today I released the Threes and Layups NBA Net Rating Calculator, an interactive web application that is an updated version of what I called the Threes and Layups Season Simulator before. To go to the app,  click the link above or click on the the link on the right side of the page under “Interactive Web Applications”.  Throughout the season, the application will be updated with up-to-date statistics.

First, a bit of background.

An NBA team’s Net Rating is simply the number of points per 100 possessions that they score (called Offensive Rating) minus the number of points per possessions that their opponents score (called Defensive Rating). A team’s Net Rating is essentially a one number summary of how well they have played.

The Threes and Layups NBA Net Rating Calculator allows you to see just how much better or worse a team would play if they improved or regressed in one of what I call the “fundamental” statistics. These statistics capture how well a team is doing in Dean Oliver’s “Four Factors”: shooting from the field, foul shooting, rebounding, and turnovers.

How to Use the App:

Step 1– Select a team from the drop-down menu where it says “Select Team”.

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Step 2– Go to “Select Stat” and choose the statistic that you want to change from the drop-down menu. Stats are labeled as either offensive or defensive. There are 14 statistics (7 on each side of the ball). Offensive 2-Pt % is the default.

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Step 3– A display will appear with the name of the statistic you want to change in bold. In the box below the name, you will see the current value of the stat for this team. Type any new value you want into the box or use the up and down arrows at the right end of the box to increase or decrease the value by 0.001 (0.1%).  Enter percents as decimals (use 0.512 rather than 51.2%). For reference, the league median value of the stat is given in parenthesis.

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Step 4– Press the “Apply Change!” button. The results will take about 5 seconds to load.

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Step 5– A box will appear below with what you changed and the results. For example, if you decreased the Buck’s defensive 3-Pt % you might see this output:

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The RESULT table tells you what would happen if the Buck’s defensive 3-Pt % decreased by 0.031 (3.1%).  Milwaukee’s defensive rating would decrease from 110.1 (24th ranked in the NBA) to 107.7 (15th ranked). The Expected Wins (out of 82) gives the number of wins the Bucks would be expected to achieve this season if they continued to play with the same fundamental stats (under “Original”) and also if they instead improved their 3-Pt % defense by the given value (under “New”). The “Dif” column is simply the New value minus the Original. The third row of the table gives estimated playoff odds. The Bucks would increase their playoff odds by 25.2 percentage points if they sustained this change over the rest of the season.


  1. The drop-down menu under “Select Display” has three options: Overall Profile, Offensive Profile, and Defensive Profile. The offensive and defensive profile options will display a table showing where the current team ranks in each of the seven fundamental offensive or defensive statistics. You can identify the team’s weaknesses (stats where a team’s rank is worse than 20th or so) and see what would happen if these areas were improved. Overall Profile, the default option gives the team’s current Net, Offensive, and Defensive Ranking, as well as their record.
  2. You should keep in mind that when you change one statistic, the application is keeping all other statistics constant. In reality, if one part of a team’s performance changed, this would likely cause ripple effects in other areas. For example, a team could increase their Offensive 3-Pt Attempt Rate by more aggressively taking contested threes early in the shot clock, but this would likely decrease their Offensive 3-Pt %. Results should be interpreted carefully.
  3. If you try to change a statistic to be below 0.05 or above 0.95 (an unrealistic value) the results will not show.
  4. All statistics are from basketball-reference, a wonderful site. Basketball-reference uses Dean Oliver’s formula for estimating possessions when computing Net Rating, so I use the same formula in my computations. The Net Rating figure from Basketball-Reference does not have “garbage time” (usually considered the last 5 minutes of a blowout) removed, so the app includes garbage time stats as well.



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